PROJECT 2: Idiopathic Pulmonary Fibrosis (IPF) is a destructive lung disease of unknown cause that has no proven therapy. IPF is associated with alveolar epithelial cell abnormalities, progressive lung scarring, and inflammation, resulting in respiratory failure and death. Studies involving individuals with the familial form of IPF, familial interstitial pneumonia (FIP), have aided understanding of genetic variations associated with progressive pulmonary fibrosis. We have previously reported two rare variants (RVs) in the Surfactant Protein C (SFTPC) gene associated with FIP. Both SFTPC RVs were found to produce altered Surfactant C proteins that were toxic to type II alveolar epithelial cells. We have also identified RVs in Telomerase genes (TERT & TERC) associated with loss of telomerase activity that cause FIP. In this project, we will investigate the hypothesis that development of IPF is influenced by multiple genetic factors that variably contribute to disease predisposition, depending on whether the variation is a rare variant (RV) of major effect or a common variant (CV) of minor effect. In combination with appropriate environmental or cellular triggers, individuals who possess these RVs and CVs may develop IPF (or FIP). In this project, we will focus on discovering and characterizing RVs of major effect that co-segregate with FIP to determine how and why they cause FIP. Identification of RVs associated with FIP will guide us towards molecular pathways that are relevant to the pathogenesis of IPF. We will utilize a combination of approaches to identify and characterize the effects of RVs in various candidate pathways in the following specific aims: 1) Characterize sequence variations in genes of the Telomerase and Surfactant Pathways as well as other select candidate genes for FIP, 2) Determine the contribution and effects of Telomerase Pathway defects to FIP, 3) Determine the contribution and effects of variations in the Surfactant Pathway and other candidate genes to FIP. Using this approach, we will elucidate genetic, cellular, and molecular pathways that are important in FIP pathogenesis.